javascript - Polymer element doesn't trigger the "on-<property>-changed" event when property changes -

i using google-sigin element polymer catalog. want listen changes signedin attribute outside polymer element. property set notify: true , in polymer documentation related change notifications, says that:

when using polymer element other elements or frameworks, can manually attach on-property-changed listener element notified of property changes, , take necessary actions based on new value.

i have tried listening on-signin-changed, on-sign-in-changed, on-property-changed, signin-changed , sign-in-changed, none of these events being triggered.

the code listens event looks like:

document.addeventlistener("domcontentloaded", function() {     document.queryselector('google-signin').addeventlistener('on-signin-changed', function() {         // never gets called     }); }); 

i know listening google-signin-success event (which works btw , can see signedin has been changed true), want understand why event isn't being triggered/what doing wrong.

cheers!

i noticed property called signedin not signin. have tried addeventlistener('signed-in-changed'?